Electrolysis of alkali metal chlorides to produce chlorine and alkali metal hydroxide has been known for a long time. In the past, hydrogen evolving cathodes have been used for this purpose. The principal chemical reaction taking place in the conventional electrolytic cell can be represented by the following scheme:2NaCl+2H2O→Cl2+2NaOH+H2 
This electrolysis reaction, having a theoretical cell voltage of 2.24 V, requires a considerable amount of energy.
Previously, oxygen consuming gas diffusion electrodes have also been used for the production of chlorine and alkali metal hydroxide, as further described in e.g. U.S. Pat. No. 4,578,159. The term “gas diffusion electrode”, as used herein, relates to an electrode comprising at least a diffusion layer and a reaction layer, to which gas diffusion electrode oxygen-containing reactant gas is supplied to undergo electrolysis. Electrolyte is supplied to one side of the electrode which is opposite to the side to which reactant gas is supplied. The principal total cell reaction taking place at the reaction layer of the electrode may be represented by the following scheme:2NaCl+H2O+½O2→Cl2+2NaOH,the theoretical cell voltage being 0.96 V, i.e. only about 40% of the cell voltage of the cell with the hydrogen evolving electrode. The cathodic oxygen reduction ½O2+H2O+2e−→2OH− has an equilibrium potential of +0.401 V, giving rise to a total theoretical difference against the hydrogen evolving electrode of 1.23 V. Therefore, the gas diffusion electrode considerably reduces the energy costs for the operation of the electrolytic cell. The control of the diffusion, however, sometimes involves problems.
An objective of the present invention is to provide an improved gas diffusion electrode with improved control of diffusion. Also, an objective of the present invention is to improve the efficiency of the electrode including the control of hydrophobicity and electrical conductivity. A further objective of the invention is to provide an electrode imparting lowered the potential, improved stability and/or current distribution.